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Monday, February 19, 2018

Record Cold and the Northwest Stays in the Freezer for a While

The air over us now is unusually cold for this time of the year, in fact, record breaking cold in some ways. For example, let's start with the temperature around 5000 ft (850 hPa pressure) at the radiosonde station at Quillayute, on the Washington Coast (see below). In this plot, the blue line shows the daily record low 850 hPa temperatures. Today's temperature (-12.5C, shown by a circle) was not only a record for the date, but the lowest for the surrounding dates as well. Really unusually cold.

The surface air temperatures last night (see below) were held up by the windy conditions (which mix down warmer air above the surface) and some clouds, but still temps dropped into the mid 20s F in much of western Washington and single digits in the mountains Some valley locations dropped below 0F. Teens dominated in eastern WA.

Tonight is going to be much colder, with colder air aloft, clear skies, and less wind. The temperatures predicted for tomorrow morning suggest mid-20s in the west and single digits east of the Cascades, with some valleys in eastern WA dropping below -8F.

The latest forecast model output predicts another four days of the really cold stuff. Here is the NWS GEFS ensemble forecast for Seattle. Several more days of lows in the mid-20s ahead.

The large scale atmospheric pattern is really locked into a super La-Nina configuration with high pressure offshore and cool northerly flow over the NW. To show you this, here are the upper level (500 hPa) weather maps for Wednesday and next Tuesday. Quite similar really.

There are occasional disturbances moving southward in to the flow east of the upper level ridge of high pressure that will bring some occasional precipitation, and in some places, snow.

To illustrate, here is the total snow fall forecast for the next 72 h. Most of the snow is heading for Oregon and SW Washington. None over Seattle or the WA Cascades.

The next 72 hour is quite different, with massive snows in the WA and Oregon Cascades. Skiers will be pleased.

6 comments:

It will be interesting to see if the medium range models verify and the cold upper trough remains over,or near,this area come next week.Historically,often in this situation the upper ridge/trough complex will continue to retrograde westward,which results in a milder southwest flow off the Pacific, and more typical mild (dull) weather.

Snow to the north...check. Snow to the west...check.Snow to the east...check.Snow to the south...check.

I don't mind a few good snowfalls per year. But life in the Convergence Zone has been very underwhelming in recent winters. The north part of the zone got hit on Sunday, but much of the zone missed out...again.

Hey Cliff I wonder if you have any comments on the extreme weather we had on Sunday, west side of Bainbridge Island. We had the strongest winds, from the north, that I have seen since 1990 - the Arctic Blast! That year our neighbors roof was partially ripped off and this felt just as strong - probably upward of 40mph? It was very scary and last a long time, from early in the morning through the night. We were without power for about 24 hours. I heard nothing mentioned on the news about it. High winds were forecast on Saturday, from the south, and we got them! But nothing was said about high winds from the north on Sunday. Do you have any data about that area during the day on Sunday?Thanks!